CVE-2021-27952Public exploit

Root access via brute-forced firmware credentials

Published Aug 3, 2021 · Updated Aug 3, 2024

Hard-coded credentials in ecobee3 lite 4.5.81.200 allow physically proximate attackers to gain root bootloader access via UART. A low-complexity root password hash stored in compiled firmware can be recovered from NAND flash and brute-forced, and the resulting password unlocks the serial console. Physical access to the obscured PCB UART and a serial adapter is required; successful access permits sensitive-data extraction or device modification.

CVSS severity9.8
Critical
EPSS probability1.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Hard-coded credentials in ecobee3 lite 4.5.81.200 allow physically proximate attackers to gain root bootloader access via UART. A low-complexity root password hash stored in compiled firmware can be recovered from NAND flash and brute-forced, and the resulting password unlocks the serial console. Physical access to the obscured PCB UART and a serial adapter is required; successful access permits sensitive-data extraction or device modification.

The record

CVE
CVE-2021-27952
Published
Aug 3, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-798, T1078.001
Attack vector
physical
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 3, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorphysical
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
5.0NIST NVDAV:N/AC:L/Au:N/C:P/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorphysical
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-798Use of Hard-coded Credentials
T1078.001Valid Accounts: Default Accounts

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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